MESCHKE, Justice.
The North Dakota Workers Compensation Bureau appealed from a district court judgment reversing the Bureau’s dismissal of Roberta Anderson’s claim as untimely filed. We affirm.
On November 7, 1984, Dr. Gregory Hen-nenfent, M.D., examined Roberta Anderson, who was experiencing various physical symptoms including numbness in her hands. One of his diagnoses was carpal tunnel syndrome, a condition of pinched nerves causing numbness in the fingers and hand. Even though she was examined on a number of later occasions, Anderson’s medical records from Dr. Hennenfent and other doctors at Mid Dakota Clinic, P.C., contain no other reference to carpal tunnel syndrome. Without interrup[498]*498tion, she continued working as a cosmetologist.
In 1994, her symptoms of carpal tunnel syndrome significantly worsened, necessitating surgery by Dr. Curtis Juhala. Anderson filed a claim for workers compensation benefits on July 18,1994. After a formal hearing, the Bureau found Anderson was “well aware that her carpal tunnel was work related as early as 1984.” The Bureau dismissed Anderson’s claim because it was not filed within one year of Anderson’s injury, as required by NDCC 65-05-01. Anderson appealed to the district court, who concluded the claim was timely and reversed the Bureau’s decision.
On appeal, we review the Bureau’s decision and not the decision of the district court. E.g., Stepanek v. North Dakota Workers Compensation Bureau, 476 N.W.2d 1, 3 (N.D.1991). Our review is limited to the record before the agency, and we do not consider the conclusions of the district court. Id. We review an administrative agency decision under NDCC 28-32-19, and it requires us to affirm the agency’s decision unless its findings of fact are not supported by a preponderance of the evidence, its conclusions of law are not supported by its findings of fact, its decision is not supported by its conclusions of law, or its decision is not in accordance with the law. E.g., White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908, 909 (N.D.1989). “In determining whether the Bureau’s findings of fact are supported by a preponderance of the evidence, we do not make independent findings of fact or substitute our judgment for that of the Bureau.” Id. at 909. Rather, as White explains at 909-10, “we determine whether the Bureau could have reasonably reached its factual determinations by the greater weight of all the evidence.”
The Bureau contends Anderson bears the burden of proving she is entitled to workers compensation benefits. However, a defense based on the statute of limitations in a civil proceeding is an affirmative defense. E.g., In Interest of K.B., 490 N.W.2d 715, 717 (N.D.1992). As McCarter v. Pomeroy, 466 N.W.2d 562, 566 (N.D.1991)(eiting 54 C.J.S., Limitations of Actions § 294 (1987)), points out: “Generally, a party relying on a statute of limitations has the burden of proving that the action is barred.”
The Bureau applied the statute of limitations under NDCC 65-05-01 as amended in 1993. However, NDCC 1-02-10 provides: “No part of this code is retroactive unless it is expressly declared to be so.” Under that rule of statutory interpretation, “[a]ll statutes enacted by the legislature are to be applied prospectively, i.e., they are to be applied only to causes of action that arise after the effective date of the statute, unless the legislature clearly expresses that they are to be applied retroactively.” Reiling v. Bhattacharyya, 276 N.W.2d 237, 240-41 (N.D.1979); see also State v. Hersch, 445 N.W.2d 626, 630 (N.D.1989). The Legislature did not direct retroactive application of NDCC 65-05-01 in its 1993 amendment. The Bureau’s findings are based on pre-1993 evidence, and it contends Anderson’s claim arose before the 1993 amendment. “Unless otherwise provided, the statutes in effect on the date of an injury govern workers’ compensation benefits.” Thompson v. North Dakota Workers’ Compensation Bureau, 490 N.W.2d 248, 251 (N.D.1992). We therefore conclude the 1993 amendment is inapplicable.
Before the 1993 amendment, the pertinent part of NDCC 65-05-01 directed:
All original claims for compensation shall be filed within one year after the injury.... When the actual date of injury cannot be determined with certainty the date of injury shall be the first date that a reasonable person knew or should have known that the injury was related to employment.
S.L.1979, Ch. 652, § 1. Under that version of the statute, the standard for determining whether a claim is timely filed “is whether or not the claimant knew or should have known that she had a compensable work-related injury.” Stepanek v. North Dakota Workers Compensation Bureau, 476 N.W.2d at 5 (emphasis in original); see also White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908. Otherwise, as White, 441 N.W.2d at 910, explains, an employee would be compelled to rush in with a claim for [499]*499every minor ache, pain, or symptom in order to make sure any future claim for compensation is not deemed untimely. Stepanek, 476 N.W.2d at 5, emphasizes: “[T]he term ‘injury1 as used in our statute must be read with reference to a ‘compensable’ injury.”
To have a compensable injury, a claimant must know or have reason to know the significance, or seriousness, of her condition and that the injury is work-related. For instance, in Stepanek, 476 N.W.2d 1, the claimant did not seek medical attention for her knee injury until the pain became disabling. We held the statute of limitations did not run during the period the claimant thought her work-related injury was minor. In White, 441 N.W.2d 908, we held the statute of limitations did not start running, even though the claimant thought he had a work-related back injury, until his injury was correctly diagnosed as a herniated disc. In Teegarden v. North Dakota Workmen’s Compensation Bureau, 313 N.W.2d 716 (N.D.1981), we noted the absence of medical advice, and held there was insufficient medical evidence showing the claimant knew or should have known his lung condition was work-related. In Evjen v. North Dakota Workers Compensation Bureau, 429 N.W.2d 418, 420 (N.D.1988), we affirmed the dismissal of a claim as untimely, but noted:
Unlike the claimant in Teegarden, Evjen received specific medical advice that his injury was
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MESCHKE, Justice.
The North Dakota Workers Compensation Bureau appealed from a district court judgment reversing the Bureau’s dismissal of Roberta Anderson’s claim as untimely filed. We affirm.
On November 7, 1984, Dr. Gregory Hen-nenfent, M.D., examined Roberta Anderson, who was experiencing various physical symptoms including numbness in her hands. One of his diagnoses was carpal tunnel syndrome, a condition of pinched nerves causing numbness in the fingers and hand. Even though she was examined on a number of later occasions, Anderson’s medical records from Dr. Hennenfent and other doctors at Mid Dakota Clinic, P.C., contain no other reference to carpal tunnel syndrome. Without interrup[498]*498tion, she continued working as a cosmetologist.
In 1994, her symptoms of carpal tunnel syndrome significantly worsened, necessitating surgery by Dr. Curtis Juhala. Anderson filed a claim for workers compensation benefits on July 18,1994. After a formal hearing, the Bureau found Anderson was “well aware that her carpal tunnel was work related as early as 1984.” The Bureau dismissed Anderson’s claim because it was not filed within one year of Anderson’s injury, as required by NDCC 65-05-01. Anderson appealed to the district court, who concluded the claim was timely and reversed the Bureau’s decision.
On appeal, we review the Bureau’s decision and not the decision of the district court. E.g., Stepanek v. North Dakota Workers Compensation Bureau, 476 N.W.2d 1, 3 (N.D.1991). Our review is limited to the record before the agency, and we do not consider the conclusions of the district court. Id. We review an administrative agency decision under NDCC 28-32-19, and it requires us to affirm the agency’s decision unless its findings of fact are not supported by a preponderance of the evidence, its conclusions of law are not supported by its findings of fact, its decision is not supported by its conclusions of law, or its decision is not in accordance with the law. E.g., White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908, 909 (N.D.1989). “In determining whether the Bureau’s findings of fact are supported by a preponderance of the evidence, we do not make independent findings of fact or substitute our judgment for that of the Bureau.” Id. at 909. Rather, as White explains at 909-10, “we determine whether the Bureau could have reasonably reached its factual determinations by the greater weight of all the evidence.”
The Bureau contends Anderson bears the burden of proving she is entitled to workers compensation benefits. However, a defense based on the statute of limitations in a civil proceeding is an affirmative defense. E.g., In Interest of K.B., 490 N.W.2d 715, 717 (N.D.1992). As McCarter v. Pomeroy, 466 N.W.2d 562, 566 (N.D.1991)(eiting 54 C.J.S., Limitations of Actions § 294 (1987)), points out: “Generally, a party relying on a statute of limitations has the burden of proving that the action is barred.”
The Bureau applied the statute of limitations under NDCC 65-05-01 as amended in 1993. However, NDCC 1-02-10 provides: “No part of this code is retroactive unless it is expressly declared to be so.” Under that rule of statutory interpretation, “[a]ll statutes enacted by the legislature are to be applied prospectively, i.e., they are to be applied only to causes of action that arise after the effective date of the statute, unless the legislature clearly expresses that they are to be applied retroactively.” Reiling v. Bhattacharyya, 276 N.W.2d 237, 240-41 (N.D.1979); see also State v. Hersch, 445 N.W.2d 626, 630 (N.D.1989). The Legislature did not direct retroactive application of NDCC 65-05-01 in its 1993 amendment. The Bureau’s findings are based on pre-1993 evidence, and it contends Anderson’s claim arose before the 1993 amendment. “Unless otherwise provided, the statutes in effect on the date of an injury govern workers’ compensation benefits.” Thompson v. North Dakota Workers’ Compensation Bureau, 490 N.W.2d 248, 251 (N.D.1992). We therefore conclude the 1993 amendment is inapplicable.
Before the 1993 amendment, the pertinent part of NDCC 65-05-01 directed:
All original claims for compensation shall be filed within one year after the injury.... When the actual date of injury cannot be determined with certainty the date of injury shall be the first date that a reasonable person knew or should have known that the injury was related to employment.
S.L.1979, Ch. 652, § 1. Under that version of the statute, the standard for determining whether a claim is timely filed “is whether or not the claimant knew or should have known that she had a compensable work-related injury.” Stepanek v. North Dakota Workers Compensation Bureau, 476 N.W.2d at 5 (emphasis in original); see also White v. North Dakota Workers Compensation Bureau, 441 N.W.2d 908. Otherwise, as White, 441 N.W.2d at 910, explains, an employee would be compelled to rush in with a claim for [499]*499every minor ache, pain, or symptom in order to make sure any future claim for compensation is not deemed untimely. Stepanek, 476 N.W.2d at 5, emphasizes: “[T]he term ‘injury1 as used in our statute must be read with reference to a ‘compensable’ injury.”
To have a compensable injury, a claimant must know or have reason to know the significance, or seriousness, of her condition and that the injury is work-related. For instance, in Stepanek, 476 N.W.2d 1, the claimant did not seek medical attention for her knee injury until the pain became disabling. We held the statute of limitations did not run during the period the claimant thought her work-related injury was minor. In White, 441 N.W.2d 908, we held the statute of limitations did not start running, even though the claimant thought he had a work-related back injury, until his injury was correctly diagnosed as a herniated disc. In Teegarden v. North Dakota Workmen’s Compensation Bureau, 313 N.W.2d 716 (N.D.1981), we noted the absence of medical advice, and held there was insufficient medical evidence showing the claimant knew or should have known his lung condition was work-related. In Evjen v. North Dakota Workers Compensation Bureau, 429 N.W.2d 418, 420 (N.D.1988), we affirmed the dismissal of a claim as untimely, but noted:
Unlike the claimant in Teegarden, Evjen received specific medical advice that his injury was related to his employment and also that it was a significant health problem. Without that advice, this would be a different case because headaches are fairly common afflictions often suffered by many from job stress. A reasonable lay person would not immediately file a claim for compensation upon learning that occasional headaches were work-related.
(Emphasis added). Grotte v. North Dakota Workers’ Compensation Bureau, 489 N.W.2d 875 (N.D.1992), and Rogers v. North Dakota Workers Compensation Bureau, 482 N.W.2d 607 (N.D.1992), are also distinguishable from Teegarden because in each of those cases, as in Evjen, the claimant had specific medical advice his injury was work-related and there was evidence the claimant was aware of the seriousness of his health problems. The majority concluded those claimants knew they had compensable injuries.
Whether Anderson knew or should have known she had a compensable injury must be determined under a reasonable person standard. See White, 441 N.W.2d at 911. In Teegarden, 313 N.W.2d at 718, we defined a reasonable person as an ordinary layperson of the same skill and knowledge as the claimant. As Teegarden at 719 illustrates, Anderson is not expected to have knowledge in medical matters comparable to a doctor.
The Bureau based its conclusion that Anderson’s claim was untimely on her medical and chiropractic records. On November 7, 1984, Dr. Hennenfent noted in Ms medical record from Ms examination of her:
She has a history of numbness in both hands wMch occur while working with her hands. She is a beautician and does a lot of hand motion. During the day her hands may feel somewhat numb and [have] decreased strength....
Positive Tanil’s sign of both wrists. There was evidence of pons weakness of both hands....
Impression: ... 2. Carpal tunnel syndrome. ...
Plan: ... Also coekup splints bilat. for h.s. for the next few wks....
Anderson began receiving chiropractic treatment from Dr. William Swanson in 1985 after being in a car accident. In Anderson’s chiropractic records, dated January 9,1985, carpal tunnel syndrome is listed as one of several complaints. Dr. Swanson noted Anderson was experiencing hand numbness.
The fact Anderson sought medical attention in 1984 does not establish she then knew or should have known she had a compensable work injury. See White, 441 N.W.2d at 911. The records prepared by Dr. Hennenfent and Dr. Swanson do not report they advised Anderson about the significance of her condition. Anderson testified she never even saw the records. A claimant is not charged with knowledge of opimons and conclusions in medical records she has not reviewed. See Teegarden, 313 N.W.2d at 719. Neither Dr. Hennenfent nor Dr. Swanson were deposed to determine what they advised Anderson [500]*500about her condition, its eventual course, or the causal connection between Anderson’s employment and her condition.
Anderson testified that she did not know her work was the cause of her injury even though she felt symptoms at work. A person who experiences minor pain or other symptoms while working does not know, or have reason to know, of a significant work-related injury. See Stepanek, 476 N.W.2d 1 (the claimant’s knee pain at work was insufficient to establish the claimant knew or should have known she had a com-pensable work-related injury). Without specific medical advice, Anderson had no reason to know in 1984 the potential seriousness of her injury or that it would become disabling ten years later. There is no evidence either Dr. Hennenfent or Dr. Swanson advised Anderson to restrict her work due to carpal tunnel syndrome.
There is no evidence Anderson missed work because of her injury before being examined by Dr. Juhala on June 30, 1994. That a person continues to work after experiencing symptoms is evidence the person is unaware an injury is a “significant health problem.” Stepanek, 476 N.W.2d at 6, n. 5. There is also no evidence Anderson incurred any significant medical expense from carpal tunnel syndrome before seeing Dr. Juhala in 1994. Without loss of work time, significant medical expense, or specific medical advice, a reasonable person would not reasonably know of a compensable work injury.
When Anderson’s injury became disabling in 1994, and she was informed by Dr. Juhala she had a compensable injury, Anderson promptly filed her claim. On this record, we conclude the Bureau could not reasonably determine Anderson knew or should have known she had a compensable injury before being examined by Dr. Juhala in June of 1994. The Bureau’s contrary finding is not supported by a preponderance of the evidence, and its conclusion that Anderson’s claim is untimely is neither supported by findings nor in accordance with the law.
We affirm the district court judgment reversing the Bureau’s denial of Anderson’s claim as untimely.